Rotating machines, such as turbine-driven generators, include bearing systems to rotationally mount the rotating parts of the machine (e.g., the rotor shaft, etc.). Over time, the bearing systems within rotating machines are subject to wear. If the bearing systems are allowed to wear too much, it can result in inoperability of the rotating machine. Depending upon the end-use of the rotating machine, its inoperability can have rather significant results.
In light of the foregoing, some rotating machines, such as turbine-driven generators installed in aircraft, include sensing systems that are configured to detect the onset of failure of the generator bearing systems. These sensing systems typically include a secondary bearing system that is isolated from electrical common during normal machine operation, when the normal (or primary) bearings are operating properly. The secondary bearing system typically includes a secondary bearing associated with each of the primary bearings. The sensing system also includes an enunciator (e.g., indicator) that, via suitable wiring, is electrically coupled in series between a power source and each of the secondary bearings. After sufficient wear of its associated primary bearing, a secondary bearing will contact circuit common, and thereby act as a switch, to electrically energize the enunciator and provide a visual warning to personnel.
Although the above-described bearing sensing systems operate generally well, these systems do suffer certain drawbacks. For example, when the enunciator is energized, personnel are unable to distinguish which of the primary bearings is worn. Present systems provide no means of determining if the enunciator has failed (e.g., burned out). Moreover, false enunciation can occur if the sensing system wiring becomes grounded. This can lead to unneeded removal from the generator prime mover and disassembly of the rotating machine.
Accordingly, it is desirable to provide a system and method of testing rotating machine bearings that allows personnel to determine which bearing is worn, and/or detects a failed enunciator, and/or is less immune to wiring grounds than present systems. The present invention addresses one or more of these needs.